Nicely done Anthony.
You've painted your Centaur the correct colour.
The Royal Marines Centaurs were painted Dark Earth which had been the standard colour for British vehicles up to late 1943.
The British switched to Khaki Drab, a slightly more green colour, in January 1944.
The RM Armoured Support Group didn't repaint their tanks in the newer colour since the tanks were originally not going to be used anywhere other than the Normandy beaches.
In the original D Day plans, the RMASG Centaurs weren't even going to have engines installed.
I've read somewhere that the tanks were turned over to French units after the Normandy beachhead had been secured.
Cheers.
jjimbo